


The Devil Inside

by kittenofdoomage



Category: Supernatural
Genre: Alpha/Beta/Omega Dynamics, Alpha/Omega, Angst, Casifer, Cheating, Claiming, F/M, Fluff, Knotting, Mating, Possessed!Castiel, Sex, Smut, Unfaithfulness
Language: English
Status: Completed
Published: 2018-05-11
Updated: 2018-05-11
Packaged: 2019-05-05 05:31:36
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,853
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14610471
Author URL: https://archiveofourown.org/users/kittenofdoomage/pseuds/kittenofdoomage
Summary: Written as a commission. The reader needs her Alpha and he's indisposed.





	The Devil Inside

You knew it wasn’t him the second you saw him.

Returning from a hunt in West Virginia, you’d found the bunker seemingly empty when you came back. The Winchesters’ scent was faint, Castiel’s even less recognizable in the air. It had been weeks since you’d seen any of them but you only wanted Castiel at that moment. You only wanted your Alpha.

The hunt had been hard and you’d been cutting it close, being out on your own in the early stages of heat, with no suppressants left to curb the need. By the time you had returned home, all you wanted was a warm bath and your bed, but instead, you were confronted with the Impala landing in the middle of the bunker, smoke rising from her engine and tires.

The occupants climbed out, Sam, Castiel, and a man you didn’t recognize. Your first instinct was to run to Cas but the instant your hands touched his face, a shock went through you and you sprang back. He looked at you, bloodied and weary, his eyes showing none of the warmth you were used to.

“You’re not Cas,” you murmured, backing up to find Sam behind you, just as another man walked into the room, obviously from somewhere in the bunker you hadn’t checked. Not-Cas rolled his eyes and grimaced.

“No, he’s not,” Sam replied, resting his hand on your shoulder. The Omega in you bristled at the touch of another Alpha before your senses recognized his scent as family. “You should go and lay down, Y/N. I can smell the heat on you.”

You nodded, turning and coming face to face with another man you didn’t recognize. “Hi,” he greeted but you were too frazzled to reply and you darted off, quickly shutting yourself in the room you’d previously shared with Cas. The room smelled only like you - there was no trace of his scent anywhere.

The agreement was simple. You helped on the small stuff, taking hunts they couldn’t and you avoided anything the Winchesters had gotten themselves into. You never felt like you were cut out for the big fight and they were quite happy to keep you away from the truly dangerous monsters. Dean had once tried to stop you hunting, to stop you from even the smallest salt and burn, but you’d turned on him.

Just because you were an Omega didn’t mean you couldn’t do something good in the world.

It was through the brothers that you’d met Castiel when he was human. When Dean said he couldn’t stay at the bunker, you’d volunteered to take him somewhere else and keep him safe, help him to adjust. It was a selfish reasoning - you’d been instantly drawn to him and it wasn’t long before your heat triggered his very first rut and Cas hadn’t hesitated to claim you as his.

Neither Winchester was happy about it because it put a bigger target on your back but you’d run with the risks and accepted everything as it came. Even when Castiel regained his grace and you barely saw him, you stayed loyal.

Now you were just confused. It smelled like Castiel but whatever was controlling him was  _ not _ your angel. That didn’t make sense to your more primeval instincts and it wouldn’t stop your heat. You took a few pain pills and a suppressant, not that it would do any good at this stage, and crawled into bed, exhaustion dragging you under.

When you woke, you weren’t alone.

Sam was in the room, with a basin of cool water and a drink, along with a few snacks. You grunted at him, rolling over onto your side, not interested in his attempts to soothe you. There was only one thing that would work and that wasn’t an option.

“Hey, Y/N,” he spoke quietly, reaching out to touch your shoulder, “you gotta eat, darlin’. Cas won’t want you getting sick.”

“That’s not Cas,” you protested, drawing further into the covers, unsure if you were hot or cold. You could feel the sweat trickling down your back, the slick between your thighs and it must have been torture for Sam to even be in the same room as you. “I want  _ my _ Alpha, Sam.”

Sam sighed, shaking his head. “I know it isn’t Cas. But we’re working on getting him back, expelling Lucifer -”

“Lucifer?” you squeaked, sitting up abruptly. “That’s  _ Lucifer _ ?” He nodded and you wailed, burying your face in your hands. “Why is Lucifer possessing, Cas? Is Cas still in there?”

“Yeah, he’s in there. And I think, or  _ we _ think, he said yes to try and figure out this thing with the Darkness. Lucifer has a better shot that the rest of us and now with God here -”

“God’s  _ here _ ?” Your eyes were wide as you sought out confirmation from Sam, who nodded. “Holy shit,” you muttered, immediately clasping a hand over your mouth. “I probably shouldn’t blaspheme, right? Will he smite me?”

“Chuck?” Sam asked, chuckling. “No, I don’t think he’d smite you for that. And he doesn’t seem to be much for the smiting anyway. Not that I’ve seen. He’s pretty… placid, actually.” You blinked at him, unsure if you were hallucinating or not. “Will you please eat something?” he implored, reaching out to touch your shoulder. “I know I can’t do much else to help but at least keep your strength up, yeah?”

Slowly, you nodded, sliding back down under the covers. Sam seemed satisfied with your answer and patted the covers, getting to his feet. You watched his back as he retreated from the room before you rolled over, dragging the sheets over your head again.

“You gonna hide in there all night?”

The voice made you sit up again and your eyes connected with Castiel’s - Lucifer’s - across the room. He was leaning against the wall, his arms folded over his chest, the trenchcoat swayed slightly around his thighs. “Lucifer,” you whispered, trembling at the scent of your Alpha so close to you. “You can’t be here.”

“Actually, I can. They,” he gestured to the closed door, “think I’m sulking in Sam’s room, playing music so loud with the door locked, that they can’t get at me.” He pushed off from the wall, walking towards you. “I must apologize for the confusion early,” he continued. “I was hurt pretty badly and you were a bit of a surprise.”

“You can’t see his memories?” you asked, tilting your head to the side. “You didn’t know he had an Omega?”

“Oh I knew,” Lucifer confirmed, smirking as he sat on the bed. “Castiel was all too clear in his need to protect you, above everything else. It’s half the reason he was interested in this cockamamie plan.” His hand was on the covers now, creeping up towards your leg. “And I can see why,” he purred.

“You’re not my Alpha,” you warned, shaking your head, even though your body didn’t know the damn difference. The room was thick with the scent of you and you had no way of knowing if Lucifer was affected like an Alpha should be. “Castiel is -”

“Right here,” Lucifer insisted, gesturing to himself. “He’s not entirely aware of our interaction but I think, being a good Alpha, he’d be fine with me servicing your needs.” His hand was on your thigh now and your entire body stiffened at the touch. “Personally, I’ve never had to deal with these pesky pheromones but being in this little angel has made me aware of so much more.”

You shook your head, wanting to back away but you were frozen in place, torn between loyalty to your Alpha and the needs of your Omega biology. “You’re not my Alpha,” you protested again, weakly this time and Lucifer smirked. “The boys will know. They’ll know and -”

Lucifer shrugged. “Guess we’ll have to go somewhere else then.”

His hand grabbed yours and you cried out, just as the room shifted and light flooded your senses. You shut them tightly, fighting off the dizziness before you could open them again. When you did, you weren’t in your room in the bunker anymore - you didn’t know where you were.

“This is better, isn’t it?” Lucifer asked, releasing his hold on you and standing up, shrugging the trenchcoat off of his shoulders, along with the jacket. You watched him warily as he tugged at his tie, loosening it and shaking his body out. “I’m still not used to this vessel.”

“Don’t talk about him like that,” you snapped, anger rising in your belly.

Lucifer chuckled. “Touchy, aren’t we?” You scowled, folding your arms across your thin tee. “I’m not going to hurt you, you know.”

“You’re hurting Cas,” you countered and the devil rolled his eyes.

“I’m really not. He’s tucked away watching cartoons.”

You blinked, unsure what to make of that. “Does he even know I’m here?”

Lucifer shrugged lazily. “Does he need to?”

“Do you know anything about humans beyond hating them?” you spat, slamming your fists into the comforter either side of you. “God, you’re an asshole.”

“Never claimed not to be,” he replied, holding his hands out to his sides. “And I know enough about humans to know that you’re in heat. Or close enough. It doesn’t take a genius to decipher the way this body responds to you.” You stared at him and he grinned directly back at you. “You’re a sweet little Omega. I can see what Cassie sees in you. You smell like peaches.”

The way he said it, in such a low purr, send a jolt of arousal shuddering through your core. “You wouldn’t know what to do with me.”

Lucifer’s grin turned lecherous and he moved towards you like a predator stalking prey. “Wouldn’t I?”

You shook your head, moving back as he crawled onto the bed, kicking his shoes off. “Stay back.”

“Make me.” Your foot shot out, aiming for his face, but Lucifer caught it, dragging you towards him as you struggled and squealed in panic. He laughed at your predicament, restraining your other leg and you fought against him. “Oh, this one’s a fighter, Castiel.”

“Get off!” you cried out, squirming in his hold. It wasn’t helpful that your body tingled with the contact, with the feel of his skin on yours. “I won’t submit to you.”

“I didn’t say I wanted you to,” Lucifer jeered, laughing harder when you tried to throw a punch at him. Your aim was off and your heat was making you as weak as a kitten. “That’s it,” he growled, pulling you closer so your legs were practically wrapped around his waist. “You’re so warm.”

“I mean it,” you shouted, striking out again. “You’re  _ not _ Castiel.”

He relaxed, taking you off guard but it gave you enough time to scramble away, landing on your feet at the other side of the bed, facing him with flushed cheeks and a heaving chest. Lucifer shifted, sitting cross-legged on the bed, watching you expectantly.

“What the hell do you want with me?” you demanded, pointing a finger at him accusingly. “I’m not  _ your _ Omega.”

“This body is your Alpha,” he retorted, still alarmingly calm. “You  _ need _ me.”

“Why can’t I talk to Castiel?”

Lucifer sighed. “He doesn’t want to talk to you. Winchesters already tried that one. He believes I can defeat Amara. ” You stood straight, raising an eyebrow. “What? I can.”

“So why are you wasting your time with me?” you asked, your voice softening. He didn’t answer and you frowned, folding your arms across your chest again. “Tell me the truth.” He still didn’t say anything and the rage in your belly started to boil again. “Goddamnit, Lucifer, tell me what the fuck is going on or I will walk out of here.”

“We’re miles from anywhere,” he pointed out.

“I don’t give a fuck.”

He laughed and you grabbed the nearest thing to hand, which happened to be a pillow and threw it at him. It bounced harmlessly off of his head and his laughter increased which just made you angrier. With a yell of frustration, you threw yourself at him, punching wildly as Lucifer kept on laughing at your actions.

You couldn’t hurt him but the small impacts of your fists against his body relieved a little of your rage and eventually, you were left straddling him, breathing heavily and almost sweating through your shirt. Lucifer’s laughter died off and he stretched his hands behind his head, smiling smugly at you.

“Feel better?”

A small snarl crossed your lips. “No.”

Lucifer’s smile only widened. “You know, I could make you feel so much better.”

“Why?” The smile faded for the briefest of seconds but you caught it and it only made you more curious about why he was pushing for this. “Seriously, Lucifer. Why the hell can’t I talk to Cas?”

He moved, shoving you off of his lap and onto the bed, moving so fast you barely had time to squeak. “You’re obstinate.”

“And you’re a dick,” you replied quickly.

“Angels are all dicks, sweetheart,” Lucifer threw out, sitting up against the end of the bed as you kneeled next to him. “And Castiel is no different.” He sighed, pinching the bridge of his nose. “God, this is like when Joey asked Rachel to get rid of his one night stand.” The reference threw you; Castiel had never watched Friends but apparently Satan did. 

“Wait,” you whispered, “does Cas not… he doesn’t want to talk to me because he doesn’t want me anymore?”

There was sympathy on Lucifer’s face and you felt like you’d hit rock bottom. “Angels and humans are very different, Y/N. We don’t have all this stupid biology for one. Most angels don’t feel this  _ intensity _ in their vessel.” He huffed, sticking his bottom lip out. “Hell, Nick didn’t feel one bit like this.”

“Castiel is my Alpha,” you murmured, shaking your head. “He… he claimed me.”

“When he was  _ human _ ,” Lucifer pointed out. “He was Alpha then. Now…” He gestured to the bulge in his pants. “He’s pretty good at turning this off. And when was the last time he was there to actually satisfy a heat?”

“I didn’t… we’ve both been…” you stuttered, unable to come up with an answer.

Lucifer gave you a pointed look. “He’s been hoping you’d seek out… assistance elsewhere. If  _ you _ did the betraying, it would break the bond. If Castiel tried, he’d just break  _ you _ .” He held his arms up. “I told you angels are dicks.”

“But he’s my Alpha -”

“No, the  _ vessel _ is the Alpha, honey. And you’re never gonna have what you need with him.”

You shook your head again, gaping at him in disbelief. It had to be a game, some kind of sick twisted joke that Lucifer was pulling to make you fall into bed with him. “I do need him.”

“Do you though?” he asked, his voice high-pitched and ridiculous. “I mean, you barely know anything about him.”

“We spent months together, when he was…”

“Human,” Lucifer interjected again. “Humans and angels are different, I think we covered that.” You were sat back on your heels now, uncaring of the discomfort where they dug into your ass. “Look, I’m just saying, like for like. You can pretend I’m him, or whatever, but you need an Alpha and -”

“But you’re still him. So, it wouldn’t work,” you announced, feeling a little proud of your loophole find.

Lucifer sucked his bottom lip between his teeth. “Yeah, it’s not about the body. It’s about who’s in charge of it.” He reached out, taking your hand and you didn’t flinch. “He loved you when he was human. But now… he’s not capable of that sort of commitment.”

It was hard to process and you still couldn’t believe it was true. You needed to hear it from Castiel, not from the devil in disguise. “Why did he leave it for so long?” you asked, your throat dry. “It’s been two years…”

Lucifer shrugged. “You’d have to ask him.”

“Well that’s no good if I can’t fucking talk to him is it?” you growled, snatching your hand away. “How about you tell him to grow a pair and get his feathery ass out here so I can kick it?” The snigger that left Lucifer’s lips made you want to punch him again and you were halfway to raising your fist when he tilted his head.

“Funny how in all these arguments, not once have you said you love him.”

You froze, your fist slowly lowering back down. “Of course I love him,” you muttered unconvincingly. “He’s my Alpha.”

“So you keep telling me,” Lucifer mused, inspecting his nails. “I mean, everything you’ve done in the last twenty-four hours was because you  _ love _ him, right? Not because your instincts are driving you to it?” You didn’t answer and his eyes flicked up to meet your crestfallen expression. “You took suppressants instead of demanding your Alpha’s attention. You avoided coming home. Let’s face it - some things just don’t work out.”

“And what the hell do you get out of it?” you enquired, eyeing him curiously.

“I get a roll in the hay with your tight little booty,” he quipped, leering at you. “Who wouldn’t want that?”

“You’re disgusting.”

“Yeah, well, call ‘em like I see ‘em.” He laughed under his breath, his eyes sparkling as he regarded you. “In all seriousness, you are one hot piece of ass.”

You grimaced, drawing back. “And you have no idea how to talk to women,” you growled back, tilting your chin up in a display of disgust. “You really think I’d sleep with you? I could… I could sleep with any Alpha.” Thinking quickly, you realized the only other Alpha you actually knew was Sam Winchester and… you shuddered. Sam was attractive but you thought of him like a big brother.

Lucifer was grinning and you narrowed your eyes, pulling a face and climbing off of the bed towards the window at the far end of the room. Looking outside, you saw the sunset over the horizon, fields as far as the eye could see.

It was actually rather pretty.

“It’s like for like,” Lucifer whispered, his voice close to your ear and despite the sudden approach, you didn’t spook. Even when his hands came to rest on your waist, you didn’t move or protest the action. “You get your freedom to find a mate who deserves you,  _ all _ of you. And I get to taste…” His lips were on your throat now, fingers pushing your hair away from your neck as he kissed along your throat. It felt so different to the way Castiel touched you.

You almost couldn’t remember the last time he did.

“It’s been a long time since I had a woman,” Lucifer murmured, kissing the ticklish spot below your ear, forcing your lips to part for the whisper of a moan he inspired. “But I don’t think I’ve ever had a woman like you.”

His fingers curled up underneath your shirt and a very small part of you still wanted to say no and cling to the memory of what you’d have with Castiel. The rest of you acknowledged the truth, outweighing the cons with the needs that your body required fulfilling.

If Castiel wanted to break the bond, then you’d break Lucifer while doing it.

Turning, you fixed a smile on the Alpha in front of you, enjoying his perplexed expression at your sudden change of demeanor. You slipped your hands up to fiddle with the collar of his shirt, undoing the top button. “Never had a woman like me, huh?” Lucifer shook his head, looking down as your hands slid down the front of his chest, nails catching on the fabric. “Maybe you should ask Castiel how  _ good _ of an Omega I am?”

His eyes widened as you slowly lowered yourself to your knees, fingers hooking in the belt buckle of his pants to tug it undone. He was already hard against the fabric, twitching when you slowly lowered his zipper, stroking the tip of his dick lightly. A wet spot appeared on the front of his boxers and you licked your lips.

“Don’t go getting too excited on me, Lucifer,” you warned, pulling his pants down so they hung around his calves. He stepped out of them, flinging them across the room with his left foot and you quickly stripped his boxers down his legs, not waiting for him to discard them as you circled his cock with your fingers. 

Lucifer groaned deeply when you pumped his length, forcing a bead of precum out of his slit, which you lapped up, keeping your eyes on him even when it hurt to look up that far. His hand came to rest on your head, not prompting your movements - he didn’t need to - but clenching ever so slightly when you took him into your mouth a little way, swirling your tongue around his tip.

You sank down further, smiling to yourself when he tipped his head back, gasping loudly at the way you took him down. His shaft pushed against the back of your throat and you willed your gag reflex down, not quite managing it but pulling back to try again. Lucifer grunted and his hips jerked, forcing his cock further into your mouth and you went with it, swallowing around him.

“Fuck,” he hissed, looking down at you with flushed cheeks, his eyes black with lust. For a second, they glowed red, and you grinned, pulling away from him. “I don’t know why he wants to give you up.”

With a shrug, you started to return to what you’d been doing but Lucifer was past the point of foreplay. He leaned down, grabbing your arm to drag you from the floor. You went willingly, despite his less than gentle touch, giggling when he practically threw you onto the bed.

“Slow down,” you murmured, arching your back when he pressed into you, sucking a purple bruise against your pulse point. “I wasn’t done.”

Lucifer growled but pulled back, looking down at you with disdain. “You’re bossy.”

“And you don’t know how to relax,” you argued, lifting yourself up on your hands. “Stand up.” He blinked and then reluctantly obeyed. You reached up, tugging at the shirt. “Take this off.” His fingers made quick work of the shirt and you groaned at the sight of Castiel’s firm stomach, the Enochian tattoo spiralling around his hip. Not wanting to leave him waiting, you stripped off your shirt, letting your breasts free and Lucifer looked down at you with a new hunger in his eyes.

You took hold of his cock again, resuming what you’d been doing before, and Lucifer snarled in his throat, unable to stop his hips thrusting forward, forcing more of his shaft between your lips. In this position, sat comfortably on the edge of the bed, it was easier to relax and deep throat him - he certainly didn’t mind the extra enthusiasm, stroking the back of your head as you sucked him off.

“You are fan-fucking-tastic,” he praised, fisting your messy ponytail in his fingers. “My baby brother is an idiot.”

There was a witty reply on the tip of your tongue but with Lucifer’s cock in the way, you couldn’t exactly voice it. Instead, you focused on what you were doing, hoping somewhere in there, Castiel knew what he was going to be fucking missing from now on.

The thought of his attempts to push you away made you angry, despite Lucifer’s valid point that you didn’t feel as much for the angel as you’d initially believed. If this was what it took to free yourself of the dependency on him, then you’d do it but you were going to damn well enjoy yourself.

Lucifer’s dick twitched in your mouth and you tasted his salty essence spurting onto your tongue. He wasn’t cumming but he was close and your pussy throbbed at the feel of his knot starting to swell. A grunt of irritation left him when you pulled away and crawled backwards onto the bed, pulling down your sleep shorts and rolling onto your belly.

He held his breath when you presented for him, lifting your ass in the air and looping one hand between your thighs to spread your pussy lips for him. Lucifer groaned, leaning forward on the bed with one knee, stroking himself as you fingered your own cunt. “Idiot,” he mumbled, shaking his head and you assumed the insult was aimed internally at your former Alpha.

“Fuck me, Lucifer,” you begged in a hiss, groaning when Lucifer settled behind you, teasing your soaked hole with his thick cock. When he pulled away, you mewled in protest, only to squeak loudly when he pressed his face against your cunt, his hands clutching your thighs. 

“Keep playing with yourself,” he groaned against you, running his tongue over your twitching hole. “I want you to cum on my tongue.”

His tongue was cooler than you expected but it felt amazing as he slid it into your body, eating you out vigorously. You cried out, clutching the sheets with your free hand as you tried to concentrate on your clit, feeling the climax building from the dual sensation of your own touch and Lucifer’s tongue.

When you did cum, you lost control, pushing back onto his mouth and he pulled away, straightening and sliding his cock home just as you were coming down from your high. It was the trigger to push you straight back to the edge and you screamed loudly, drowning out his moan of pleasure when your pussy spasmed around his dick.

He was cursing now but you were too far gone, mouth slack against the sheets as Lucifer drove into you, chasing his own pleasure. “Never felt… so fucking warm and soft… and wet…” the words dissolved for a second, “can’t… fucking… gonna knot you.”

You could feel it, the thick ring of muscle at the base of his cock catching with each thrust and you pushed back, desperate for it. Lucifer’s hips stuttered and he thrust once more, hard enough to make you cry out, before his knot lodged inside you, his cum a warm gush against your cervix.

When he finally finished, he collapsed, groaning with the exertion as he tried to keep his weight off you. The realization that he’d probably never knotted an Omega before made you grunt and shift, pushing him until you were on your side and he instantly curled up against you, his body pliable and warm.

There was a dull ache in your chest as you realized the bond to Castiel had been broken and the tears that filled your eyes were unwelcome. Lucifer was already softly dozing behind you, wiped out from the sex and after a few moments, he pulled away, his knot slipping free of your cunt, leaving a trail of cum across your thighs.

You didn’t want to go back to the bunker, not smelling of sex with an Alpha who wasn’t yours anymore. After two years, suddenly being unclaimed again was a heavy weight in your belly. Despite Lucifer being in the driver’s seat, it was Castiel’s scent that clung to you and you had a sudden urge to shower.

Slipping from underneath Lucifer’s arm, you padded around the room, finding the closet door to actually be the door to an ensuite shower room. Locating a towel, you retrieved your clothes from the floor and shut the door behind you, turning the shower on.

Spending longer than necessary underneath the hot spray, you washed away the scent that covered your skin and the cum between your thighs, trying not to cry. You didn’t want to weep over this, not when you could start again. Forcing a silver lining onto those clouds was hard but you could do it.

The door opened and Lucifer moved into the bathroom, naked with a confused look on his face. “Oh, there you are,” he muttered, closing the door again when he realized you were in the shower. “I was worried.”

That was unexpected. You frowned at him through the clear curtain, unsure why he would worry. “What?”

He shrugged. “You weren’t there and… I was worried.”

You didn’t believe him. Even if you did, his time in Castiel’s vessel was limited - getting attached to another angel Alpha who would just discard you wasn’t on your list of approved stupidity this week. “I needed a shower. When can we go back to the bunker?”

Lucifer frowned. “When your heat is done.”

“I’m good,” you insisted and he chuckled.

“Obstinate,” he reaffirmed his insults from earlier. “You think I’m going to give you up?”

You stared at him as he pulled the curtain to one side and stepped into the tub with you. “What are you doing?”

Lucifer grinned, backing you against the wall and the arousal between your legs returned, the heat in your belly overwhelming your better judgement. “Staking a claim,” he informed you, before crushing his mouth to yours.


End file.
